Even back then, it could play more than one stream. You had to have a sound card or kernel drivers that supported it (and all non-obsolete ones did by the time pulse audio came out).
I still don’t know what purpose pulseaudio serves, other than adding latency and making stuff less reliable.
PipeWire is better, but it turns out you can just use OSS under freebsd these days, and everything just works, but with lower latency.
If you have some sort of potato sound card that can’t mix output channels in hardware, note that OSS added sw mixing by 2007 (with support for 16 channels by default).
Nonsense - HDA systems were overwhelmingly the majority of Linux systems at that point, and didn't have any hardware support for multiple streams. OSS with software mixing was a commercial product that wasn't upstream. ALSA had userspace mixing but it was very much not an out of the box experience, and didn't take advantage of hardware capabilities in the way Pulseaudio did to reduce wakeups and power consumption.